1. Field of the Invention
The present invention relates to track scales with uninterrupted, continuous rails which are supported in a weighing section of line on several weighing sleepers.
2. Description of the Related Art
The purpose of such track scales is to weigh railway wagons as they travel over the weighing section of line. In the interests of adhering to a preset weighing precision it is important that the wagons do not vibrate as they travel over the weighing section of line, because this would effectively falsify the weighing result. Accordingly, a long straight section of track is required into which the weighing section of line is incorporated. In this particular region the track bed should be as uniformly elastic as possible so as not to excite any vibrations.
Furthermore, the line nay not exhibit any shocks in this region. The influence of leading and trailing wheels Is considerable and must be detected in principle by the weighing system. Changes in the rigidity of the track bed may not cause any increase in the calibration error.
In the case of known track scales of the type initially described (U.S. Pat. No. 4,170,268) the sleepers in the vicinity of the weighing section of line are designed as special weighing sleepers. They essentially comprise double-T bearers which are laminated with wire Strain gauges and are supported at their ends on a relatively large rail bed comprising steel-reinforced concrete.
The bending strain of the double-T bearers detected by the wire strain gauges delivers a mass of the weight forces acting on the rails by way of the wagon wheels.
Since the line of rail runs uninterrupted, it is necessary to record those portions of the weight transferred by the rails in the non-measuring normal sleepers adjacent to the weighing section of line, which represent a power shunt for weighing.
In many cases such track scales are incorporated into a line of rail as a subsequent measure, whereby the continuous rails remain Intact. To incorporate the weighing sleepers the track bed in the vicinity of the weighing section of line must be partly removed and then replaced after the weighing sleepers have been set in. This means a change in the rigidity of the track bed in the vicinity of the weighing section of line. The larger deformations in the rail in this section are the cause of undesired vibrations of the wagons which render measuring results inaccurate.
Even when the track scales are not added at a later date, but are incorporated during railway construction, the substantially greater structural height of the weighing sleepers of the known track scales, as compared to the normal sleepers, indicates a changed rigidity in the track bed in the vicinity of the weighing section of line.
In the case of the known track scales direct application of the wire strain gauges to the double-T bearers of the weighing sleepers leads to increased susceptance to failure, because it is very difficult to protect these wire strain gauges adequately against environmental influences. Besides, the material of the double-T bearers or of the rails is little suited as a deformation body for a sensor contributing to the weighing process. The necessity of having to apply the wire strain gauges under unfavourable conditions on site also impedes attainable weighing accuracy.
The double-T bearers of the weighing sleepers serving as weighing elements are relatively large components whose handling poses difficulties during manufacture. Their rigidity is relatively low, since they are stressed according to the bending beam principle. This too can lead to substantial deviation In the rigidity of the line of rail in the vicinity of the weighing section of line compared to the adjacent regions. Disengaging disturbances, such as moments of flexion and transverse forces, are not possible on the double-T bearers, or only inadequately so. The dimensions of the double-T bearers make their capacity to be tested more difficult.
The operating procedures required on site at time of assembly of the track scales, in particular the application of the wire strain gauges, result in highly expensive and lengthy assembly, requiring prolonged blocking of the section of rail concerned. Subsequent shifting of the track scales is possible only at considerable expense.
The object of the present invention is therefore to produce track scales of the type described at the outset, such that they can be incorporated into a section of rail easily and inexpensively by having their components prefabricated to the greatest possible extent and in particular such that there is no change in rigidity influencing the weighing result in the vicinity of the weighing section of line.
This task is solved by the present invention in that, in terns of their height and width, the weighing sleepers correspond to the normal sleepers which have been replaced in the weighing section of line and respectively exhibit two weighing cells supporting both rails, and in that transverse force sensors arranged at the ends of the weighing section of line are prefabricated measuring elements introduced into a transverse borehole of the rail stem.
The effect of the weighing sleepers in terms of height and width adapting to the normal sleepers is that due to exchange of the sleepers there is no change to the native ballast underneath the sleepers and accordingly no change in the rigidity of the ballast underneath the weighing section of line, as compared to the adjacent ballast. This applies in particular where the track scales are Incorporated at a later date into an existing section of rail But even when the track scales are already provided when the section of rail is being laid the constant external dimensions of the normal sleepers and of the weighing sleepers mean that the structure and the dimensions of the track bed are identical in the vicinity of the weighing section of line and in the adjacent areas, so that there is no change In rigidity in the vicinity of the weighing section of line.
All measuring elements used for the weighing procedure, namely the weighing cells in the weighing sleepers and the transverse force sensors set into the transverse boreholes of the rail stems, can be manufactured using customary manufacturing methods ensuring high measuring accuracy and can be checked prior to installation. Independent of the condition and manufacturing quality of all the weighing sleepers weighing cells are used for weighing which are optimised for this application and in particular are free from interfering moment of flexion influences and transverse force influences.
All components of the track scales can be easily dismantled without damage and reused at another site. This enables the track scales to be relocated at relatively low expense.
According to a preferred embodiment of the invention provision is made for each weighing sleeper to exhibit a sleeper housing, on whose housing floor the weighing cells are supported which project through openings on the upper side of the sleepers and bear the rails. This creates an arrangement of the weighing cells which has considerable protection, whereby the external contours and dimensions of the weighing sleepers can be adapted to the normal sleepers to the greatest extent possible.
In particular, it is an advantage for the sleeper housings to at least display an external contour corresponding to the normal sleepers which are replaced in the weighing section of line on the housing floor and the connecting side walls of the housing.
An embodiment of the invention will now be explained In greater detail hereinbelow as illustrated in the diagram, in which: